This invention relates to a heatable vehicle window (e.g., vehicle windshield, backlite, or the like) including a substantially continuous heatable layer(s), wherein offset voltages or electric potentials are used to achieve approximately uniform heating.
Heatable windows are known in the art. For example, see U.S. Pat. Nos. 3,893,234 and 5,229,205, the disclosures of which are hereby incorporated herein by reference. Conventional heatable windows for vehicles typically include first and second conductive bus bars in electrical contact with a conductive coating including an electroconductive layer. The first bus bar is usually provided at a top portion of the window, and the second bus bar at a bottom portion of the window.
Herein, the word xe2x80x9ctopxe2x80x9d when used to describe a bus bar or conductor means that the bus bar or conductor is at least partially located in the top half of the window. Likewise, the word xe2x80x9cbottomxe2x80x9d means that the bus bar or conductor is at least partially located in the bottom or lower half of the window.
The electroconductive layer, at a location between the bus bars, generates heat when electric current is passed therethrough via the bus bars. In such a manner, snow and ice may be melted from vehicle windows such as windshields, backlites, sidelites, and/or the like. Windows may also be defogged in such a manner.
In recent years, devices such as rain sensors and/or toll devices have become desirable in vehicles such as cars, trucks, sport utility vehicles (SUVs), and the like. Rain sensors and/or toll devices are often mounted within the vehicle proximate a top portion of the windshield (e.g., near where rearview mirrors are sometimes located). Rain sensors and/or toll devices typically transmit and/or receive signals (e.g., infrared signals (e.g., 880 nm), RF signals, electromagnetic signals, etc.) through the windshield. Accordingly, it is undesirable to position signal inhibiting structures such as metal bus bars and/or conductive coatings in areas of a windshield through which such signals must be transmitted/received by rain sensors and/or toll devices. Unfortunately, if one were to simply modify the shape of the upper bus bar in a conventional heatable windshield to loop around the rain sensor and/or toll device area (e.g., see FIG. 2), then hot spots would tend to develop at corners/curved areas of the upper bus bar as the windshield is heated (i.e., the current flow is not approximately uniformly distributed).
In view of the above, it will become apparent to those skilled in the art that there exists a need in the art for a heatable window design which enables current flow to be approximately uniformly distributed and/or which enables approximately uniform heating of the window, so as to reduce the likelihood of overheating and enable efficient heating of the window.
An object of this invention is to provide an efficient bus bar arrangement for a heatable vehicle window (e.g., windshield, sidelite, or backlite).
Another object of this invention is to provide a heatable vehicle window including a bottom bus bar and a plurality of top bus bars. Voltages or electric potentials applied to the top bus bars are offset or different, so that a first one of the top bus bars is at a given electric potential and another one of the top bus bars is at a different electric potential (i.e., the voltages/potentials are offset from one another). The degree to which the top bus bar voltages are offset relative to one another is a function of the distance each respective top bus bar is from the bottom bus bar across the heatable layer(s). Given a substantially continuous heatable layer(s), this enables approximately uniform heating of the window.
Another object of this invention is to provide a heatable window design which is capable of accommodating a rain sensor and/or toll device coating deletion area, without being susceptible to a high likelihood of significant overheating.
Another object of this invention is to fulfill one or more of the above-listed objects.
Generally speaking, certain example embodiments of this invention fulfill one or more of the above-listed needs or objects by providing a vehicle window comprising:
a conductive layer supported by a substrate;
wherein a first voltage V1 is applied across the conductive layer via first and second bus bars, and a second voltage V2 is applied across the conductive layer via said first bus bar and a third bus bar; and
wherein the second bus bar is spaced further across said conductive layer from said first bus bar than is said third bus bar, and wherein V1 greater than V2.
In certain preferred example embodiments, the first and second voltages V1 and V2 are selected in accordance with equation of d2/d1=V2/V1, where d1 is a distance across the conductive layer between the first and second bus bars, and d2 is a distance across the conductive layer between the first and third bus bars.
In other embodiments, the instant invention fulfills one or more of the above listed needs and/or objects by providing a heatable vehicle window comprising:
first and second substrates laminated to one another via at least one polymer inclusive interlayer;
a coating including at least one heatable conductive layer supported by said first substrate and extending across at least a portion of a viewing area of the window;
a bottom bus bar and first and second different top bus bars, each of said bottom and top bus bars being in electrical communication with said at least one heatable conductive layer; and
wherein first and second different voltages are applied to said heatable conductive layer via said first and second top bus bars, respectively, in order to heat said heatable conductive layer.
In other example embodiments, the instant invention fulfills one or more of the above-listed needs by providing a method of heating a vehicle window including first and second substrates laminated to one another via at least one interlayer, with at least one heatable conductive layer supported by said first substrate, the method comprising:
applying different voltages across said conductive layer via first and second different bus bars in order to heat at least part of the vehicle window.
This invention will now be described with respect to certain example embodiments thereof as illustrated in the following drawings, wherein: